Kyungwha Park (Virginia Tech)

Date: Mon. September 25th, 2023, 12:45 pm-1:45 pm
Location: Rock 221 (Foldy) & Zoom
Website: http://www1.phys.vt.edu/~kyungwha/kpark/park.html

Effects of disorder and hydrogenation in intrinsic magnetic topological insulators

Kyungwha Park

Department of Physics, Virginia Tech

Abstract:
Topological insulators have gapless Dirac surface states that are protected by a topological invariant in the presence of time reveral symmetry. When time reversal symmetry is broken, the Dirac surface states are gapped and interesting features are expected such as quantum anomalous Hall (QAH) effect, topological magnetoelectric effect, and axion physics. In particular, when ferromagnetic order is formed within topological insulators (i.e., magnetic topological insulators) in zero magnetic field, the QAH effect can be realized for the chemical potential tuned within the surface gap such that the Hall conductance is quantized and chiral charge currents flow around the edges without dissipation. Recently, a MnBi2Te4 intrinsic magnetic topological insulator and  related superlattices have been shown to exhibit the QAH effect around 1-2 K. This temperature is much higher than the temperature where the QAH effect was first observed in Cr-doped (Bi,Sb)2Te3 topological insulators.

In this talk we investigate the electronic structure and magnetic properties of MnBi2Te4/Bi2Te3 superlattices with a focus on the effects of structural composition, Bi vacancies, and Mn disorder, by using density functional theory (DFT) including the on-site Coulomb repulsion (Hubbard) U term for Mn 3d orbitals. Our results are compared to electron transport and angle-resolved photoemission experiments. We also present the effects of hydrogenation and disorder on the electronic structure, magnetic order, and magnetic anisotropy for MnSb2Te4 by using the DFT+U method and compare to experiments.

 

Host: Shulei Zhang